Systems And Methods For Scanning A Beam Of Charged Particles

ABSTRACT

Systems and methods of an ion implant apparatus include an ion source for producing an ion beam along an incident beam axis. The ion implant apparatus includes a beam deflecting assembly coupled to a rotation mechanism that rotates the beam deflecting assembly about the incident beam axis and deflects the ion beam. At least one wafer holder holds target wafers and the rotation mechanism operates to direct the ion beam at one of the at least one wafer holders which also rotates to maintain a constant implant angle.

RELATED APPLICATIONS

This application claims priority to provisional application Ser. No.61/089,362 filed Aug. 15, 2008, and provisional application Ser. No.61/089,378 filed Aug. 15, 2008, both incorporated herein by reference.

BACKGROUND

The manufacture of semiconductors typically includes a number of ionimplant steps whereby a workpiece, usually a silicon wafer, is presentedto an impinging ion beam. The velocity of the ions is set such that theywill bury into the workpiece and come to rest at a desired depth,forming an implanted region or layer. The ion beam in almost all casesis smaller than the silicon wafer and measures must be taken to implantthe entire wafer surface. The ion dose must be uniformly distributedover the wafer surface and preferably every ion will impinge the wafersurface at the same angle.

In a typical ion implanter, a relatively small cross section beam ofdopant ions is scanned relative to a silicon wafer, which can be done inessentially one of three ways: scanning of the beam in two directionsrelative to a stationary wafer; scanning of the wafer in two directionsrelative to a stationary beam; or a hybrid technique where the beam isscanned in one direction while the wafer is mechanically scanned in asecond, typically orthogonal, direction. In all cases, the ability toimpinge the wafer at selectable non-zero angles of incidence withminimum angle spread is required.

Each technique has advantages and disadvantages. A widely used approachhas been to mount a batch of wafers on a disc or at the end of spokes ona rotating wheel which causes a fixed direction ion beam to impinge uponeach wafer in turn. The rotating disc or wheel is then scanned to andfro and causes the fixed direction ion beam to impinge upon every partof the surface of every wafer. This technique has proven successful withsmaller wafer sizes but is less attractive with today's larger wafers.

For implantation into larger (300 mm) wafers, batch processing iscurrently not preferred because the individual work-in-process value ofeach wafer introduces a significant financial risk, should a problemarise during implantation which causes a batch to be scrapped. Anotherreason batch processing is not preferable is because production flow issimplified for non-batch processing, especially for wafer lot sizeswhich do not match the batch number for a particular wheel. Stillanother reason is that single wafer implanters avoid implant angleerrors that are inherent in wheel type batch implanters built to-date.Two-dimensional electrostatic or magnetic scanning of an ion beam inorthogonal directions relative to a stationary wafer is a process thathas been implemented in early-generation commercial implanters, butmodern implanters require all the ions to be traveling in as closely aspossible parallel paths, which is increasingly difficult as wafer sizesgrow (especially for two-dimensional scanning). Present single-waferscanning techniques tend to employ so-called hybrid scanning, where theion beam is scanned or formed into a stationary ribbon by electrostaticor magnetic means in a first direction that is perpendicular to the beamline axis in the ion implanter, and the wafer is mechanically moved in asecond, generally orthogonal, direction. In each case, the apparatus toeither scan and restore the beam to a parallel condition or mechanicallyscan the wafer have problematically grown very massive, expensive, andcomplex as wafer sizes have increased to the present 300 mm wafer size,and this problem will increase as wafer sizes increase in the future.

There are significant advantages (in terms of cost,footprint—minimization of the length of the beam line, weight, and lowermechanical complexity) if a much simpler, more compact and lower costscanning system is employed. These advantages can be used to producecost effective, application specific, implanter tools, which can beoptimized for one or just a few implant process steps. In this way, theever increasing complexity and performance compromises of broad rangeimplanters is avoided. For example, one implanter may be optimized forlight ions at moderate energies such as is required for high-dosehydrogen implanting for layer separation and another implanter may beoptimized for low energy high-dose boron such as is used in source/drainor source/drain extension implants. Other examples could optimizeperformance for higher energy low-dose or cluster ion beams such asdecaborane or GCIB (Gas Cluster Ion Beam).

U.S. Pat. No. 4,295,048 discloses a system of deflecting electrons to aplurality of discrete positions using a series of sequentially operatedmagnets arranged along a beam pipe. The electron beam is deflected byeach magnet in turn to an electron window associated with each magnet.U.S. Pat. No. 6,617,586 also discloses a system for deflecting anelectron beam, in this case a pulsed electron beam, to a plurality ofdiscrete positions using a series of sequentially operated magnets.However, both of these systems are only suitable for deflectingelectrons to discrete positions, and do not allow for continuousscanning of a charged particle beam to produce a uniform dosage across atarget wafer. Furthermore, both systems are only described in relationto electron beams, and in the case of U.S. Pat. No. 6,617,586,specifically to pulsed electron beams.

It is therefore an object of the present invention to provide scanningof the beam of charged particles across a target surface in a continuousmanner, to provide for uniform dosage of particles across the surface,or at least to provide the public with a useful choice.

SUMMARY OF THE INVENTION

The following embodiments provide a variety of novel beam management(i.e., generation, scanning, focusing) methods and devices that can beoptionally employed to tailor a simple low cost small footprint ionimplanter architecture (FIG. 1 a) to particular ion species, beamcurrent, energy, and throughput performance ranges, while preserving thebasic implanter architecture and a large number of common parts. While aprimary goal of beam management technology, the following embodimentsare not limited to only the illustrated architecture, and may have otherapplications, some of which are described.

Non semi-conductor doping ion implant applications, such as layerseparation, materials modification, and photovoltaic devices, may besuited to the methods and systems described herein, which areparticularly adaptable to large work pieces, but which may also beadaptable to other materials.

In an embodiment, a system for scanning a beam of charged particlesacross a target surface includes a beam source for producing a beam ofcharged particles along an incident beam axis; a beam deflector,positioned on the incident beam axis, for deflecting the beam of chargedparticles away from the incident beam axis towards the target surface;and a rotation mechanism coupled to the beam deflector to rotate thebeam deflector about the incident beam axis.

In an embodiment, a method for scanning a beam of charged particlesacross a target surface includes the steps of: providing a beam ofcharged particles along an incident beam axis; providing a beamdeflector on the incident beam axis, for deflecting the beam of chargedparticles away from the incident beam axis towards the target surface;and rotating the beam deflector about the incident beam axis to scan thebeam across the target surface.

In an embodiment, an ion implant apparatus includes an ion source forproducing an ion beam along an incident beam axis; a beam deflectingassembly for receiving and deflecting the ion beam; a rotation mechanismcoupled to the beam deflecting assembly for rotating the beam deflectingassembly about the incident beam axis; a first wafer holder for holdingtarget wafers; and a second wafer for holding target wafers. Therotation mechanism is operable to direct ion beam at the first waferholder and the second the wafer holder.

In an embodiment, a system for scanning a beam of charged particlesacross a target surface includes a beam source for producing a beam ofcharged particles; and a beam deflector. The beam deflector includes aseries of individually controllable deflecting elements arranged along abeam path, and a control means coupled to each of the deflectingelements. The control means is operable to control the deflectingelements to provide for a substantially continuous sweep of the beam ofcharged particles across the target surface.

In an embodiment, a method of scanning a beam of charged particlesacross a target surface using a series of individually controllabledeflecting elements arranged along an incident beam axis includescontrolling each of the deflecting elements to provide a travelingmagnetic or electric field. The traveling field moves along the axis ofthe incident beam to provide a substantially continuous scan of theincident beam.

In an embodiment, a charged particle beam scanning apparatus includes abeam scanner for scanning a beam of charged particles in a firstdirection, and a beam focusing assembly positioned to receive the beamof charged particles from the beam scanner. The beam focusing assemblyhas a series of individually controllable deflecting elements arrangedalong the first direction. The beam focusing assembly focuses the beamin the first direction.

In an embodiment, a method of focusing a beam of charged particlesscanning in a first direction includes the steps of: providing a seriesof individually controllable beam deflecting elements arranged along afirst direction; and controlling each of the deflecting elements tofocus the beam as it scans across the series of deflecting elements.

In an embodiment, an apparatus for multi-directionally scanning a beamof charged particles across a target surface includes a beam source forproducing a beam of charged particles, a beam scanner for scanning thebeam of charged particles in a first direction; a beam deflector fordeflecting the beam of charged particles; and a linear actuator coupledto the beam deflector for moving the beam deflector in a seconddirection to provide beam scanning in the second direction.

In an embodiment, a multi-directional charged particle beam scanningapparatus has a beam source for producing a beam of charged particlesalong an incident beam axis. A beam deflector deflects the beam ofcharged particles. A linear actuator coupled to the beam deflector movesthe beam deflector along the incident beam axis, and a rotation drivemechanism coupled to the beam deflector rotates the beam deflector aboutthe incident beam axis.

In an embodiment, an apparatus for multi-directional scanning of acharged particle beam includes a beam source for producing a beam ofcharged particles along an incident beam axis. A beam scanner scans thebeam of charged particles in a first direction. A beam deflectorreceives the beam of charged particles from the beam scanner. Electrodesdisposed with the beam deflector extend in the first direction, toreceive the beam throughout scanning and to deflect the beam of chargedparticles. A linear actuator coupled with the beam deflector moves thebeam deflector to scan the beam in a second direction.

In an embodiment, a method for bi-directionally scanning a beam ofcharged particles includes: scanning a beam of charged particles in afirst direction; and moving a beam deflector in a second direction,non-parallel with the first direction, to scan the beam in the seconddirection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a schematic representation according to a first embodiment.

FIG. 1 b is a cross-section of the embodiment shown in FIG. 1 a.

FIG. 2 a is a schematic representation according to an embodiment.

FIG. 2 b is a cross-section of the embodiment shown in FIG. 2 a.

FIG. 3 is a schematic representation according to an embodiment.

FIG. 4 a is a schematic representation of a deflector assembly for useaccording to an embodiment.

FIG. 4 b is an end view of the deflector assembly shown in FIG. 4 a.

FIG. 5 a is a schematic representation according to an embodiment.

FIG. 5 b is a cross-section of the embodiment shown in FIG. 5 a.

FIG. 6 is a flow chart depicting a method for scanning a beam of chargedparticles across a target surface, according to an embodiment.

FIG. 7 a is a plan view of a dual-chuck layout for mounting wafers forscanning, according to an embodiment.

FIG. 7 b is a second angle projection of the dual-chuck layout of FIG. 7a.

FIG. 7 c is a third angle projection of the dual-chuck layout of FIG. 7a.

FIG. 8 a is a schematic representation of an ion implanter including thedual-chuck layout of FIGS. 7 a-7 c, according to an embodiment.

FIG. 8 b is a cross-sectional view of the implanter of FIG. 8 a.

FIG. 9 a shows a ring arrangement for supporting and transferring abatch of wafers, according to an embodiment.

FIG. 9 b is a side view of the ring arrangement of FIG. 9 a.

FIG. 9 c shows the arrangement of FIG. 9 a, mounted with non-circularworkpieces in lieu of wafers.

FIG. 10 is a schematic view of an implanter architecture having acluster of the implanter systems of FIG. 8 a.

FIG. 11 is a schematic diagram of an ion implant system according to anembodiment.

FIG. 12 a is a plan view of a deflector assembly according to anembodiment.

FIG. 12 b is an end cross section of the deflector assembly shown inFIG. 12 a.

FIG. 12 c is a side cross-section of one side of the deflector assemblyshown in FIG. 12 a.

FIG. 13 is a geometrical schematic relating to a basic method ofobtaining continuous scanning from an array of discrete bending elementsaccording to an embodiment.

FIG. 14 a is a plan view of an implanter architecture including adeflector assembly as shown in FIGS. 12 a-12 c.

FIG. 14 b is a cross-section of the implanter architecture shown in FIG.14 a.

FIG. 15 illustrates an alternative deflector assembly according to anembodiment.

FIG. 16 a illustrates a further alternative deflector assembly accordingto an embodiment.

FIG. 16 b shows a cross-section of the assembly shown in FIG. 16 a.

FIG. 17 a illustrates a focusing function of a deflector assembly inconjunction with a deceleration arrangement according to an embodiment.

FIG. 17 b is an end view of the arrangement of FIG. 17 a.

FIG. 18 illustrates a deflector assembly used for focusing a chargedparticle beam according to an embodiment.

FIGS. 19 a and 19 b show the deflector assembly of FIG. 18 incombination with a deceleration arrangement.

FIG. 20 illustrates a neutral stop arrangement according to anembodiment.

FIG. 21 shown one exemplary scanning (sweep) magnet where the mainscanning effect results from time varying of distance, according to anembodiment.

FIG. 22 shows the scanning magnet of FIG. 21 in conjunction with asecond “corrector” pole array, according to an embodiment.

FIG. 23 shows the scanning magnet of FIG. 21 arranged in conjunctionwith a corrector magnet, according to an embodiment.

FIGS. 24 and 25 show an exemplary configuration whereby the magnetreturn yoke is configured as a largely closed iron box in order to trapX-rays injected into the magnet from the ion source port, according toan embodiment.

FIGS. 26 and 27 describe a very simple implanter with an absoluteminimum of components achieved by combining a spinning wafer chuck withan angular scan to implement a linear scan, according to an embodiment.

FIG. 28 shows one exemplary deflector assembly where some of the magnetpoles are split at the incoming beam centerline, according to anembodiment.

FIG. 29 is a schematic illustration of an implant system incorporating asecond embodiment of a scanning system according to an embodiment.

FIG. 30 is a cross-section of the implant system of FIG. 29.

FIG. 31 is another cross-section of the implant system of FIG. 29.

FIG. 32 is a schematic illustration of a scanning system, according toan embodiment.

FIG. 33 is a cross-section of the scanning system of FIG. 32.

FIG. 34 is a schematic illustration of a scanning system, according toan embodiment.

FIG. 35 is a cross-section of the scanning system of FIG. 34.

FIG. 36 is a flow chart illustrating a method of for scanning a beam ofcharged particles in two non-parallel directions according to anembodiment.

FIG. 37 is a flow chart showing a method for multi-directional scanningof a charged particle beam according to an embodiment.

FIGS. 38, 39, and 40 illustrate the deflector of FIG. 29.

DETAILED DESCRIPTION

FIG. 1 a shows an exemplary architecture of an ion beam implanter system100 for implanting target wafers with ions. Implanter system 100(hereinafter also referred to as “implanter 100”) includes an ion beamsource 10 and an analyzer magnet 12. Analyzer magnet 12 is shown asformed from a series of discrete magnetic elements, but it may be of aconventional type. An ion beam 11, shown as a line, formed by ion beamsource 10 passes through analyzer magnet 12 and, after passing through aresolving aperture, enters a beam deflector assembly 13. Ion beam 11 mayrepresent any type of charged particle beam. Deflector assembly 13 is,for example, a magnetic assembly formed from a series of individuallycontrollable deflector elements. In an embodiment, at least one of thedeflector elements is an electromagnet. Alternately, each individuallycontrollable deflector element is an electromagnet. In anotherembodiment, at least one of the deflecting elements is an electrodeplate.

Deflector assembly 13, for example, includes two rows of opposing coils23 wound around a series of poles 22. Rows of coils 23 can be seen inthe view of FIG. 1 b. Coils 23 are arranged in a row that extends in thedirection of incoming ion beam 11. The deflector elements can becontrolled to provide, in effect, a traveling magnetic field that isused to deflect the ion beam to scan it over a target surface.

Deflector assembly 13 is aligned with the axis of incident ion beam 11.The yoke on which the deflector assembly is mounted is rotatable aboutthe axis of incident ion beam 11 using a rotational drive mechanism 15.Rotational drive mechanism 15, for example, rotates deflector assembly13 to direct beam 11 towards, and scan beam 11 across, a target surfacesuch as a surface of a wafer. Rotational drive mechanism 15 may be asuitable drive mechanism, such as a servo motor.

Implanter 100 includes a wafer chuck 14 for holding and tilting a targetwafer 36. Wafer chuck 14 is mounted within a processing vacuum chamber16. Chuck 14 is tilted under the control of a tilting drive 17. Tiltingdrive 17, for example, controls tilt of the wafer depending upon arotational position of deflector assembly 13, such that beam 11 isincident on the target surface (e.g., a wafer 36 surface). A controlmeans (which may be a servo system linking drive elements 15 and 17 ormechanical linkage) is used to coordinate the tilt angles of wafer chuck14 and deflector assembly 13 in order to maintain a precise angle ofincidence of ion beam 11 impinging upon wafer 36. This implant angle isillustrated as ninety degrees, but may be preset prior to starting animplant process to any angle, and the preset angle should remainconstant during the entire angular beam scan. Alternatively, the implantangle may be varied during an implant process. For simplicity purposesonly, circular wafers are described. It will be appreciated by one ofordinary skill, after reading and comprehending the present Application,that workpieces (targets) may be any shape.

Beam deflector assembly 13 provides beam scanning in the direction ofincident ion beam 11. FIG. 1 a shows ion beam 11 scanned to threedifferent positions, 11 a, 11 b, and 11 c. Scanning in a seconddirection is provided by the rotation of deflector assembly 13 about theaxis of incoming beam 11. The traveling magnetic field may provide afast scan at about 10-100 Hz, and the mechanical, rotational scan mayprovide a slow scan at about 0.5 Hz. The angle through which therotational scan travels depends on the dimensions of the target (e.g.,the wafer surface) and the distance between the target and deflectorassembly 13. In an embodiment, deflector assembly 13 rotates through+/−25°.

In order to keep the angle between the target surface and ion beam 11constant across the scan, wafer chuck 14 may be controlled to rock insynch with rotation of deflector assembly 13. This motion is illustratedmore clearly in FIG. 1 b.

FIG. 1 b is a cross sectional view along the line A-A shown in FIG. 1 a.It can be seen that the wafer can be tilted to maintain ion beam 11 atnormal incidence throughout the scan. Also shown in FIG. 1 b is a beamdump 21, to which ion beam 11 is directed when the wafer is beingreplaced. Beam dump 21 may extend the full length of deflector assembly13 and may be used for beam diagnostics. A “straight through” beammeasuring position 20 is also provided to measure and set up the beamwith the scanner off.

FIG. 1 a also shows components for moving wafers to and from wafer chuck14. Wafers are loaded into a load lock 19, for example, through a slitvalve. A wafer transfer assembly 18 moves the wafer to chuck 14. Whenion implantation of the wafer is complete, wafer transfer assembly 18moves the wafer back to load lock 19 and the wafer is removed via theslit valve.

FIGS. 2 a and 2 b illustrate an alternative architecture ion beamimplanter 200. FIG. 2 a is a plan view of implanter 200 and FIG. 2 b isa cross-sectional view along the line A-A of FIG. 2 a. Implanter 200includes features of implanter 100; accordingly, these features arenumbered as in FIGS. 1 a and 1 b. Implanter 200 additionally includes asecond ion beam source 25 and a corresponding second analyzer magnet 26.Second ion beam source 25 produces a second incident ion beam 211, whichenters second analyzer magnet 26. Second analyzer magnet 26 is alignedwith deflector assembly 13 so that upon exiting second analyzer magnet26, second ion beam 211 enters deflector assembly 13 along its axis ofrotation, in the same manner as ion beam 11 from ion beam source 10. Itis often desired to implant different ion species into a single wafer.Using implanter 200, it is possible to switch quickly between ion beamsources 10 and 25 by switching respective analyzer magnets 12 and 26 onand off Ion beam sources 10 and 25 may be kept hot, that is, ready forimmediate use. While only two ion sources are shown in FIG. 2 a, it willbe appreciated by one of ordinary skill, upon reading and comprehendingthe present Application, that any number of ion sources may beincorporated in the architecture of implanter 200.

Implanter 200 also includes a second target position on the oppositeside of deflector assembly 13 to the first target position (e.g., atchuck 14). At the second target position, there is a tilting wafer chuck24 for holding a second wafer, a tilting drive 17, and an associatedwafer loading and unloading equipment 28, 29, described below. Deflectorassembly 13 not only rotates to provide a slow scan across each wafer,it may also rotate through 180° to implant the second target (i.e., asecond wafer) once the first target implant is complete. In other words,rotational drive mechanism 15 may rotate deflector assembly 13 to directbeam 11 towards, and scan beam 11 across, a wafer held by either chuck14 or by chuck 24. While the second target is being implanted, the firsttarget (i.e., first wafer) can be unloaded from chuck 14 and replacedwith a new target. Any number of target wafer stations can be providedaround deflector assembly 13 using this architecture. Ion beamdiagnostics may be provided at beam dump 21 between the two targets orat a “straight through” position 20 that ion beam 11 impinges on whendeflector assembly 13 is not energized.

In FIG. 2 a, second chuck 24 is shown rotated approximately 90° from theimplant position, for unloading of a wafer secured at chuck 24 through aload lock assembly 29. Load lock assemblies 19, 29 are shown arrangedparallel to one another; however, they may be in a desiredconfiguration, to interface with a wafer handling assembly or clustertool.

A number of different deflector assemblies may be used with the abovedescribed implanters. A deflector assembly may provide scanning of beam11 and/or 211 in a direction substantially parallel to the incoming (orincident) beam axis, as described above. Alternatively, a deflectorassembly may provide no further scanning beyond a rotational scan aboutthe incoming beam 11/211 axis. In such a case, the target wafer may bemoved to provide scanning over the entire wafer surface. In addition,the wafers may be scanned in two dimensions and the rotation of thedeflector assembly may be used only to move the ion beam (e.g., beam 11or 211) from one target position to another.

As discussed above, the deflector assembly (e.g., beam deflectorassembly 13) may provide beam scanning via a series of individuallycontrollable deflecting elements (e.g., opposing coils 23 withcorresponding sets of poles 22) arranged along a beam path that includesthe deflector. Beam deflector assembly 13 illustrates sixteen suchelectromagnets. In the condition when all electromagnets are equallyenergized, ion beam 11 will be subject to a generally uniform magneticfield and will bend according to beam position 11 a. If the first tenelectromagnets are turned off, but all others remain on, beam 11 willtravel further into the magnet array of assembly 13 before becomingsubject to the magnetic field, and will bend according to position 11 b.A controller such as a computer coupled to each of the deflectingelements may coordinate the adjustment of the deflecting elements toprovide for a substantially continuous sweep of the beam of chargedparticles (e.g., beam 11) across the target surface.

Alternately or additionally, beam scanning means may be provided by alinear actuator that moves the deflector assembly along the incidentbeam axis (i.e., a linear actuator that moves beam deflector assembly 13along the axis of beam 11). Deflector assembly 13 may electrostatic, forexample, including an electrostatic mirror or a pair of curved electrodeplates, or deflector assembly 13 may be magnetic.

FIG. 3 shows an ion beam implanter 300. Implanter 300 includes featuresof implanters 100 and 200. For simplicity, shared features are indicatedusing the same reference numbers Implanter 300 has an electrostaticdeflector assembly 33, formed from two parallel arrays 34 of electrodeplates 35 (only one array 34 is visible in FIG. 3, however, the secondarray is positioned above the array shown with a gap between the arraysto allow the beam to travel between them. Since the pairs of plates 35positioned above and below the beam are at the same electric potential,an equipotential is formed across the beam gap provided the gap issmall. For larger gaps, a grid is typically used to bridge the gap andcreate the equipotential, while still allowing the beam through. Acharged particle beam, such as ion beam 11, travels between arrays 34.Corresponding plates 35 of each array 34 are held at the same electricpotential, but successive sets of plates 35 are sequentially energizedto different potentials resulting in a field gradient that causes thebeam particles to deflect. Plates 35 effectively act as a travelingelectrostatic mirror and deflect the charged particles (e.g., of ionbeam 11) as a result of an electric field generated between successiveadjacent plates 35 in each array 34.

As shown in FIG. 3, plates 35 are angled at 45° relative to incident ionbeam 11. However, it will be appreciated by one of ordinary skill, afterreading and comprehending the present Application, that other plate-beamangles may be chosen in order to selectively deflect ion beam 11 (i.e.,through different angles).

By controlling the voltage applied to each plate 35, deflected ion beam11 scans in the same manner as described and shown with respect todeflector assembly 13 of FIGS. 1 a, 1 b, 2 a, and 2 b. Ion beam 11 isshown in three positions 11 a-11 c in FIG. 3. A smooth scan may beachieved by using a suitable control strategy, i.e., energizing aplurality of adjacent plates 35 within each array 34 at any one time.Electrostatic deflector assembly 33 may be mounted with a yoke androtated or translated in the same manner as beam deflector assembly 13of FIGS. 1 a, 1 b, 2 a, and 2 b.

FIGS. 4 a and 4 b show one deflector assembly 45 for use in implanters100, 200, or 300, in accordance with an embodiment. FIG. 4 a is a sideview of deflector assembly 45. FIG. 4 b is an end view of deflectorassembly 45.

Deflector assembly 45 includes a C-shaped yoke 40 around which one ormore coils 41 are wound to provide a magnetic field. Yoke 40 is formedfrom a material with a high magnetic permeability, for example, from amaterial used to form a magnetic core. Traveling magnetic pole pieces 42slide along yoke 40 and provide an area of reduced clearance betweenopposing faces of yoke 40. Pole pieces 42 have a higher magneticpermeability than air and vacuum. Thus, the magnetic field generated bycoils 41 is concentrated in yoke 40, pole pieces 42, and in the spacebetween the pole pieces (see FIGS. 4 a and 4 b). The magnetic fieldbetween pole pieces 42 is, for example, used to bend ion (or electron)beam 11. By moving pole pieces 42 along yoke 40, ion beam 11 can be madeto scan. In practice, measures would be taken to minimize the influenceon the beam of stray magnetic field between the yoke arms by minimizingthe stay field magnitude and employing magnetic shielding to protect thebeam. Pole pieces 42 may be mounted with yoke 40 using air bearings orother mountings that counter the magnetic attraction between yoke 40 andpole pieces 42. Various arrangements (not shown) may be used to maintainion beam 11 in a vacuum. Pole pieces 42 are shown attached to linearmotors 43, which are mounted on yoke 40, and which drive pole pieces 42to achieve a desired scan.

Deflector assembly 45 may be coupled to a rotation mechanism andincorporated into an implanter architecture, such as implanters 100,200, and 300, described above. Alternately, other deflector assembliesmay be incorporated into implanters 100-300. For example, anelectrostatic beam deflector with a single pair of arcuate or spherical(spherical plate inflector), nested electrode plates may be mounted witha linear actuating mechanism, such as a linear motor, moving along theaxis of the incident ion beam (i.e., beam 11) to provide for a beamscan.

Such an arrangement is schematically illustrated in FIGS. 5 a and 5 b.FIG. 5 a is a schematic representation of an implanter 500, and FIG. 5 bis a cross sectional view of implanter 500. The basic architecture issimilar to that shown in FIGS. 1-3, and some of the features sharedbetween implanters 100-300 and 500 are indicated using same referencenumbers.

Implanter 500 includes ion beam source 10 and an analyzer magnet 52.Analyzer magnet 52 is, for example, of a conventional type. Ion beam 11passes through analyzer magnet 52 and, after passing through a resolvingaperture 50, enters a beam deflector assembly 53. Typically, an“electrostatic mirror” (not described here) or a “spherical plateinflector” would be of a conventional type known in the art. The beamdeflector assembly 53 is, for example, an electrostatic deflectorincluding a spherical plate inflector separated into two sections inorder to create a deceleration/acceleration gap 54 part way around theinflector curvature. The ion beam 11 is deflected part of the totalangle by the action of the electrodes 59 and 60 and deflected thebalance by the action of electrodes 57 and 58. In between these twodeflection stages the beam energy is decreased (or increased) by anelectric field gradient formed in the gap 54. In practice, one or moreelectron suppression electrodes would most likely be located in thedeceleration/acceleration gap. For clarity of illustration, suppressionelectrodes are not shown in FIGS. 5 a and 5 b.

The deflector assembly 53, as shown in the partial-section illustrationFIG. 5 a, appears to be arc segments but in practice are nested sectionsfrom the surface of spheres of a predetermined radius. Curvature of thearc segments in the direction orthogonal to the deflection plane isillustrated in FIG. 5 b. Alternatively, an array of plates or meshforming a similar spherical geometry may be used to facilitate vacuumpumping in gap 54 and minimize beam-strike for neutral or off-energycharged particles. An electric potential is set up between the inner andouter spherical sections to provide an electric field transverse to theion beam direction, which deflects ion beam 11 through 90°. Otherdeflection angles can be achieved by this technique. The electric fieldmagnitude required varies depending upon the ion beam energy and can beeasily calculated.

In order to scan ion beam 11 across the target wafer, deflector assembly53 undergoes both linear and rotational movement. The linear movementtranslates the deflector assembly 53 along the axis of the incoming beamand is so illustrated in FIG. 5 a by depicting the deflector assembly 53in a second location as deflector assembly 53 a to represent the extentsof the linear translation. Deflector assembly 53 is, for example,mounted with a linear and rotational drive mechanism 55. As shown inFIG. 5 a, deflector assembly 53 deflects ion beam 11 through 90° andmoves along the axis of incoming ion beam 11 to scan beam 11 across thetarget wafer parallel to the axis of incoming beam 11. Deflectorassembly 53 rotates about the incoming beam 11 axis to scan beam 11across the wafer in a direction perpendicular to the incoming beam 11axis. It is likewise possible to use deflector assembly 53 to deflection beam 11 through a different angle, and to provide the target waferat a different inclination to deflected ion beam 11.

Alternatively, deflector assembly 53 may be a single electrostatic ormagnetic deflector that is stationary, apart from rotation about theaxis of incoming beam 11. In this case, the target wafers can be movedto provide scanning over the entire wafer surface. Additional elementsmay be included in implanters 100-300 and 500 to provide for beamfocusing and filtering.

Rotation of deflector assemblies may provide any of implanters 100-300and 500 with a compact, flexible, and scalable architecture that canincorporate two or more target wafer positions to provide for highthroughput. Particular deflector assemblies may be chosen to suitparticular applications. For example, when high beam current/low beamenergy implant is required, a magnetic deflector assembly might be used.When low beam current/high beam energy is required, an electrostaticdeflector assembly might be more suitable. The architecture describedherein allows for the simple addition of further ion sources, and mayalso be modified or provided as a retrofit assembly to interface withexisting wafer handling equipment.

While the concepts described generally refer to various forms of linearbeam scanning combined with rotational beam scanning, which is coupledwith synchronized wafer tilting to maintain a fixed implant angle, itshould be noted that the linear scan effectively forms a ribbon beamwhich is swept over the wafer by the rotational scan. Ribbon beamscreated by other means could also be used to achieve similar benefits inimplant tool simplicity and cost. The linearly scanned beam mayalternatively remain fixed and the wafer can be translated through theribbon so as to expose the entire wafer. Also, the linear scan may beeliminated in the case where the wafer is rotated so that the beameffectively implants an annulus on the wafer surface and the rotationalbeam scan would then cause the annular exposure to change in radiusuntil the entire wafer is exposed.

While the work-piece is described in this document as a wafer forsemiconductor manufacture, other targets may be implanted by adaptingthe holder and work-piece handling to suit desired applications.

FIG. 6 is a flow chart depicting a method 600 for scanning a beam ofcharged particles across a target surface. A beam of charged particlesis generated along an incident beam axis, in step 62. The beam ofcharged particles is deflected away from the incident beam axis andtowards a target surface, in step 64. In one example of steps 62 and 64,ion beam 11 is provided by ion beam source 10 along an incident beamaxis that intersects deflector assembly 13. Deflector assembly 13 isadjusted, e.g., via rotational drive mechanism 15, to deflect beam 11toward wafer chuck 14 holding a target wafer.

The beam is scanned across the target surface in step 66. For example,rotational drive mechanism 15 rotates deflector assembly 13 to scan beam11 across the wafer surface (see, e.g., FIGS. 1 a-3). Step 66 may befollowed by one or more of optional steps 68-72 (indicated by dotted box65). In step 68, the target surface, e.g., the wafer, is tilted basedupon a rotational position of the beam deflector to achieve apredetermined angle between the beam and the target surface. In oneexample of step 68, tilting drive 17 tilts wafer chuck 14 depending uponposition of deflector assembly 13, so that beam 11 strikes the targetwafer at a predetermined angle throughout a scan. A feedback loop (notshown in FIGS. 1 a-6, for ease of illustration) between deflectorassembly 13 and/or rotational drive mechanism 15 and tilting drive 17may be employed for automatically tilting wafer chuck 14 (and a securedwafer) to achieve and maintain the desired angle throughout a scan.

In optional step 70, the deflector is rotated to direct the ion beam toa second target surface. In one example of step 70, rotational drivemechanism 15 rotates deflector assembly 13 to direct incident ion beam11 towards second wafer chuck 24, to which a second wafer is secured. Asdescribed with respect to step 68, above, tilt of wafer chuck 24 may beadjusted to achieve and maintain a desired wafer-to-beam anglethroughout a scan. For example, wafer tilt drive 27 may communicate withrotational drive mechanism 15 and, based upon a position of deflectorassembly 13, tilting wafer chuck 24 to achieve a predeterminedwafer-to-beam angle.

In optional step 72, the beam is scanned in a direction substantiallyparallel to the incident beam axis. In one example of step 72, deflectorassembly 53 (FIGS. 5 a and 5 b) deflects ion beam 11 through 90° andmoves along the axis of incoming ion beam 11 to scan beam 11 across thetarget wafer parallel to the axis of incoming beam 11.

FIGS. 7 a-7 c illustrate alternate views of a dual-chuck system 700, forholding and transferring two wafers 710 (or other workpieces) through anangular scan. System 700 includes two wafer chucks 712. For example, asshown in FIGS. 7 b-7 c, wafer 710 a is mounted with chuck 712 a, andwafer 710 b mounts with chuck 712 b. In one embodiment, chucks 712 a,712 b are e-chucks, which electrostatically clamp a wafer or otherworkpiece, to hold it without mechanical clamps. Chucks 712 a, 712 bmount with arms 714 a, 714 b, respectively, which then connect with aturntable 716. Turntable 716 rotates one chuck 712 into a horizontalwafer load position while the other chuck 712 is exposed to a scanningbeam. For example, FIG. 7 b shows chuck 712 a positioned for exposure toa beam 718 for linear scanning, while chuck 712 b (not shown beneathwafer 710 b) is in a horizontal wafer load position. FIG. 7 c is a thirdangle projection of 7 b showing chuck 712 b in the horizontal wafer loadposition, while wafer 710 a is scanned by beam 718 in an angular scan.

System 700 achieves scanning and loading with very little dead-timebetween wafers. A finished wafer (e.g., 710 b, FIGS. 7 b and 7 c) isunloaded and a fresh wafer loaded onto a chuck which is stationary in ahorizontal orientation, while the other chuck (e.g., chuck 712 a) isexposed to the beam. The angular scan during implant can be quite slow,for example, in the range of 0.5 to maybe 3 Hz, so a fairly simplemechanism will hold the stationary wafer still for load/unload.

The throughput of an implanter is strongly affected by implant dead-timewhich occurs any time during which the beam is not impinging upon thewafer. Provided the wafer exchange can be completed in a time less thanor equal to the implant time, which would be typically the case for highdose implants, wafer exchange will occur almost entirely in thebackground, resulting in maximum beam utilization. With system 700, thedead-time to exchange chucks may be very short, resulting in only asecond or two between the finish of one implant and the start of thenext. For very low implant doses where the implant time can be as shortas a few seconds, the exchange time is commonly longer than the implanttime for most implanters on the market today.

FIGS. 8 a and 8 b show an ion beam implanter system 800 for implanting atarget (e.g., a wafer) with ions Implanter system 800 (hereinafter alsoreferred to as “implanter 800”) includes an ion beam source 810 and ananalyzer magnet (beam analyzing magnet) 812. Analyzer magnet 812 isshown as a 60° magnet of traditional style could also be formed from aseries of discrete magnetic elements, as described above. The ion beam811, indicated by a line, is formed by ion beam source 810 and passesthrough analyzer magnet 812 and, after passing through a resolvingaperture, enters a beam deflector assembly 813, formed as a travelingfield beam-scan magnet. Beam deflector assembly 813 is, for example, amagnetic assembly formed from a series of individually controllableelements. In one embodiment, at least one of the elements is anelectromagnet. Alternately, each individually controllable element is anelectromagnet. In another embodiment, at least one of the elements is anelectrode plate.

Beam deflector assembly 813, for example, includes two rows of opposingcoils 823 wound around a series of poles 822 (see FIG. 8 b). Poles 822are arranged in a row that extends in the direction of incoming ion beam811. The individually controllable elements can be controlled toprovide, in effect, a traveling magnetic field that is used to deflection beam 811 to scan it over a target surface (such as a wafer 710,described with respect to FIGS. 7 a-7 c).

Beam deflector assembly 813 is aligned with the axis of incident ionbeam 811. The yoke on which the deflector assembly is mounted isrotatable about the axis of incident ion beam 811 using a rotation drivemechanism 815. Rotation drive mechanism 815 for example rotates beamdeflector assembly 813 to direct ion beam 811 towards, and scan ion beam811 across, a target surface such as a surface of wafer 710. Rotationdrive mechanism 815 may be a suitable drive mechanism, such as a servomotor. A straight-through beam measuring cup 820 measures beam strengthand/or angle.

Implanter 800 includes dual-chuck system 700, for positioning a targetwafer secured with a chuck (e.g., wafer 710 a mounted with chuck 712 a)for ion implantation, while a second chuck (e.g., chuck 712 b, obscuredby wafer 710 b) is positioned for wafer loading/unloading. In anembodiment, a loadlock or cluster wafer delivery tool 814 transferswafers 701 to and from chucks 712. Wafers are loaded intoloadlock/delivery tool 814, for example, through a slit valve (notshown). A wafer transfer assembly 819 moves wafer 710 to chuck 712. Whenion implantation of the wafer is complete, wafer transfer assembly 819moves the wafer back to loadlock/delivery tool 814 and the wafer isremoved via the slit valve. In the case of a cluster wafer deliverytool, transfer assembly 819 may be the central wafer transport devicethat is incorporated into such tools.

As illustrated in FIG. 8 a, system 700, with chucks 712 a, 712 b, ismounted within a processing vacuum chamber 816. Turntable 716 is rotatedunder the control of a rotating drive 717, which, for example, controlsrotation of chucks 712 a, 712 b. Chucks 712 a, 712 b may tilt upon arms714 a, 714 b under control of a tilting drive 719, which, for example,controls tilt of the wafer depending upon a rotational position of beamdeflector assembly 813 and/or turntable 716, such that ion beam 811 isincident on the target surface (e.g., wafer 710 a).

Beam deflector assembly 813 provides beam scanning in the direction ofincident ion beam 811. FIG. 8 a shows ion beam 811 scanned to threedifferent positions, 811 a, 811 b, and 811 c. Scanning in a seconddirection is provided by the rotation of beam deflector assembly 813about the axis of incoming ion beam 811. The traveling magnetic fieldmay provide a fast scan at about 10-100 Hz, and the mechanical,rotational scan may provide a slow scan at about 0.5 Hz. The anglethrough which the rotational scan travels depends on the dimensions ofthe target (e.g., the wafer surface) and the distance between the targetand beam deflector assembly 813. In an embodiment, beam deflectorassembly 813 rotates through +/−25°.

In order to keep the angle between the target surface and ion beam 811constant across the scan, wafer chucks 712 may be controlled to rock insynch with rotation of beam deflector assembly 813.

FIG. 8 b is a cross sectional view of implanter system 800. As shown,mounted wafer 710 can be tilted to maintain ion beam 811 at normalincidence throughout the scan.

Conventional implanters are either “single wafer” or batch. Batchimplanters were developed to facilitate higher throughput at higherdoses, basically by increasing the total workpiece area in order todistribute heating by the ion beam. Particularly at high beam currentand/or high beam energy, workpiece temperature limits these conventionalimplanters. Since the beam is delivering electrical energy to theworkpiece (beam current x beam energy), wafer heating results, due tothe beam total power and power density arriving on the wafer.Traditional batch implanters use a “disc” array with a number of wafersmounted on pedestals which are arranged in a ring and inclined withrespect to the plane of the “disc.” The disc rotates at quite high speed(up to 1200 rpm) and wafers are successively exposed to a spot beamwhich is very much smaller than the size of each wafer. The wafers clampto their respective inclined pedestals due to centrifugal force. Thecentrifugal clamping prevents the wafers from flying off and helpsconduct heat delivered by the beam away via the pedestal. A secondscanning direction is implemented by translation the spinning discslowly back and forth. Thus an array of wafers (workpieces) is exposedto two approximately orthogonal scanning motions and the whole waferarray is implanted.

FIG. 9 a shows a ring arrangement 900 of a batch of wafers that is muchsmaller than conventional batches. Ring arrangement 900 includes a setof five spokes 902 with e-chucks 912 at the end of each, each e-chuck912 supporting a wafer 910 (e-chucks not visible beneath wafers 710; seeFIG. 9 b). The disc rotation (indicated by motion arrow 914) is now theslow scan (compared to conventional batch implanters today whererotation is the fast scan) since the fast traveling field scanner iseffectively creating a line or ribbon beam 915 through which eachsuccessive wafer 910 passes as ring arrangement 900 rotates. A change inangular orientation of each wafer 910 occurs as it passes through theline scan. Also, if the angular speed (rotation) of the disc isconstant, the effective scan speed of each wafer 910 as it is exposed tothe line beam will vary across the wafer in the circumferentialdirection. These undesirable motions can be compensated by counterrotating each wafer 910 so that there is no effective angle change asthe wafer passes through the line beam and the circumferentialnon-uniformity can be compensated by a cosine function applied to thedisc rotation so that each wafer 910 has uniform velocity as it passesthrough the beam or by varying the length or frequency of the line scanas each wafer 910 passes. Since only slow rotation of the disc isrequired, and thus negligible centrifugal force, e-chucks 912 can beused to hold each wafer 910, resulting in superior wafer cooling. Sinceeach wafer 910 rotates individually, as indicated by rotation arrows916, the orientation of wafers 910 can be changed without removing them,facilitating “quad” implants (a series of four implants with each waferrotated 90 degrees in between). Angled implants will be done by tiltingthe whole disc (i.e., ring arrangement 900) and loading will be done bytilting the disc (i.e., ring arrangement 900) all the way to horizontal.Thus, the small batch implant geometry resulting has all the desirablefeatures of a single wafer implanter, but much more workpiece area todissipate beam power.

Traditional batch implanters have well known disadvantages due to theincline angle, workpiece angle change with respect to the beam, and highdisc rotation speed generating particles which have been proven to causedamage in some delicate implant steps. Ring arrangement 900 avoids thesedisadvantages. FIG. 9 c depicts the same features shown in FIG. 9 a, butillustrates rectangular workpieces 918 in lieu of circular wafers 910,shown in FIG. 9 a.

FIG. 10 shows an ion implanter architecture 1000 with a cluster ofimplanters, specifically, multiple implanter systems 800 with dual-chucksystems 700. As shown, two loadlocks or cluster delivery tools 1002accept wafers or other workpieces and transfer the wafers or workpiecesto an in-vacuum wafer transport 1004, from which the wafers orworkpieces are shuttled to implanter systems 800, for example via asemi-standard port 1006. See, e.g., description of loadlock/deliverytool 814 for exemplary functioning of loadlocks 1002. Implanter systems800 are, for example, high-dose hydrogen and/or helium implanters, toprovide layer separation. Alternately, semi-standard port 1006facilitates connection to other process stations, such as metrology,layer transfer processing, hydrogen and/or helium implant-bond-cleave,and wafer or handle (the substrate to which the separated layer isbonded) cleaning or preparation steps. The low cost, compactapplication-specific nature of ion implanter architecture 1000facilitates a complete cycle layer transfer system that includes allrequired process steps, including separation and bonding in order toproduce layer transfer end products in a single cluster tool.

The demand for very high beam currents in order to get good productivityfor this process is getting sufficiently great that evenstate-of-the-art beam current levels are not enough. In addition, wafercooling creates more and more complexity. An alternative is architecture1000 with its cluster of low-cost, dedicated implanter systems 800 toachieve very high production capability for high dose implants, forexample, as used for silicon layer separation, while staying withinpresently available beam generation and wafer cooling technology. Themost widely used ion species for silicon layer separation is hydrogen,but in some cases a lesser, but still high, dose of helium ions isadded. A cluster tool with a number of hydrogen implanter systems 800plus a helium implanter system 800 avoids the present practice ofseparate implant steps on different machines with the complexities ofwafer handling and transporting in between. The purpose of layerseparation implants is to create a buried layer of hydrogen or otheratoms which enable the thin silicon layer through which the implantedions have passed to be separated from the bulk of the wafer. This thinlayer of silicon is then usually bonded to another wafer or othersubstrate surface. In addition to the clustering of ion implant tools asdescribed, process chambers for bonding and the separation (also knownas “cleaving” or “exfoliating”) steps as well as wafer cleaning,metrology, or other process steps, can lead to improved production yieldand equipment and process economies.

Clustering of an ion beam implanter system 800 with a plasma ionimplantation tool (not shown) is an example where clustering of low-costdedicated ion implant tools could lead to other advantages, for example,boron source-drain implants by plasma doping as well as the associatedbut angle critical source-drain extension by system 800 could besequenced on a cluster tool 1000 including intermediate steps withoutthe wafers leaving the clean controlled vacuum environment. Combiningimplant with other process steps is at least difficult and generallyimpractical with traditional implanters because they are so large andcomplex. While layer separation is a particular target of interest, manyother applications can benefit from combining steps, which becomespractical once the implanter is sufficiently simplified.

FIG. 11 is a schematic view of an ion implant system 1100 according toan embodiment. System 1100 includes an ion beam source 1110, ananalyzing magnet 1111, a deflector assembly 1112, a deflector control1113, and a target wafer holder 1114 (e.g., a wafer chuck). An ion beam1115 is indicated by a line. Although system 1100 is described withrespect to ion implantation, system 1100 and other innovations describedherein may be used with a charged particle beam, such as an electronbeam.

Deflector assembly 1112, for example, bends ion beam 1115 through anangle, e.g., 90° or 270°. Deflector assembly 1112 has a series ofindividually controlled deflectors arranged along the path of incidention beam 1115. The individual deflectors each provide either a magneticfield or an electric field across the path of ion beam 1115. Using anappropriate control scheme, deflector assembly 1112 produces a bendingfield (either magnetic or electric) that moves along the axis ofincident ion beam 1115, which is accomplished by controlling themagnitude of the field generated by each of the individual deflectorsand by using a plurality of individual deflectors at once.

At least one of the individually controlled deflectors may be anelectromagnet. The electromagnets may be formed using superconductingcable. In one embodiment, each individually controlled deflector is anelectromagnet, and the electromagnets arranged at about 45° to incidention beam 1115, for beam deflection through 270°. Alternately, some orall of the deflecting elements may be electrode plates. Deflectorassembly 1112 is, for example, operable to energize a plurality ofindividually controlled deflectors simultaneously.

FIG. 12 a schematically shows one embodiment of deflector assembly 1112.Deflector assembly 1112 includes two rows of opposing coils 1221 woundaround a series of poles 1224. Only one row of coils 1221 can be seen inthe view of FIG. 12 a. Coils 1221 are arranged in a row that extends inthe direction of incoming ion beam 1115. FIG. 12 a illustrates sixteensuch electromagnets. In the condition when all electromagnets areequally energized, ion beam 1115 will be subject to a generally uniformmagnetic field and will bend according to beam path 1115 b. If the firstten electromagnets are turned off, but all others remain on, beam 1115will travel further into the magnet array of assembly 1112 beforebecoming subject to the magnetic field, and will bend according toposition 1115 a. Each coil 1221 may have an associated power supply 1222mounted on the same yoke 1223 as the coils and poles 1224. However, inaddition or alternately, a remotely mounted power supply 1222 may beconnected with coils 1221 by suitable wiring. A controller, such as acomputer coupled to each of the deflecting elements, may coordinate theadjustment of the deflecting elements to provide for a substantiallycontinuous sweep of the beam of charged particles (e.g., beam 1115)across the target surface.

Yoke 1223 is, for example, a mechanically movable structure, adapted torotate about the axis of incoming ion beam 1115. Yoke 1223 is, forexample, rotatable between two target positions or to sweep the scannedbeam ribbon 1115 a-1115 b over a workpiece. Alternately or additionally,yoke 1223 is translatable. At least one power supply 1222, for poweringthe individually controlled deflectors, mounts with yoke 1223. Yoke 1223may additionally include cooling means for cooling the individualdeflectors (e.g., electromagnets).

FIG. 12 b is a cross-section of deflector assembly 1112 as shown in FIG.12 a, looking along the direction of incident ion beam 1115. FIG. 12 bshows opposing sets of coils 1221, positioned on either side of the pathof ion beam 1115 to provide a magnetic field through which ion beam 1115passes. A power bus bar 1225 is also shown in FIG. 12 b. Power isdelivered through power bus bar 1225 to the power supplies 1222.Similarly, control signals may control each power supply 1222 to adjustthe current supplied to coils 1221, and hence the strength of themagnetic field generated by each coil 1221.

FIG. 12 c is a cross-section of one row of coils 1221 and poles 1224.FIG. 12 c shows more clearly that, in one embodiment, each coil 1221 iswound around a separate pole 1224 and that the whole array of poles 1224is mounted on a yoke 1223.

FIG. 11 and FIG. 12 a each show ion beam 1115 deflected to two differentbut parallel paths 1115 a and 1115 b. The path (1115 a, 1115 b, or analternate path) to which ion beam 1115 is deflected depends on the fieldgenerated by deflector assembly 1112. The magnetic field can effectivelybe made to travel up and down deflector assembly 1112 to scan exitingion beam 1115 across a range of parallel paths.

Rather than simply switching coils 1221 on and off in a sequentialfashion, a control strategy may be used to provide a smooth scan of ionbeam 1115 by using a plurality of coils 1221 at the same time. The pathof beam 1115 can be thought of as being made up of a set of n contiguousbend segments, each segment corresponding to a coil 1221. If each coil1221 produces a predetermined field, then a predetermined bend angle isachieved after beam 1115 passage through exactly n bend segments. Tocause output beam 1115 to scan, the set of bend segments is decrementedby one at the entry and incremented by one at the exit, so that the bendis always occurring in n segments. This results in a scan with beam 1115exiting discontinuously at the end of successive bend segments.

However, it is desirable that beam 1115 scan in a continuous fashion formost applications, which can be achieved by adjusting the fields in thevarious segments so as to make output beam 1115 exit some fraction0<(k)<1 of the way across the last of the segments which areparticipating in the bend. By making k a function of time, k(t), andprogramming the scan system so that k(t) varies with time continuouslyfrom zero to unity, the scan can be made continuous across the entirearray of segments. This is illustrated in graph 1330, FIG. 13.

One possible general expression for the relationship between the bendradii and bend angles in the segments 1 to n+1 when the desired bendangle is 90° is in the form of two equations:

$\begin{matrix}{{r_{1} + {\left( {r_{2} - r_{1}} \right)\cos \; \alpha_{1}} + {\left( {r_{3} - r_{2}} \right){\cos \left( {\alpha_{1} + \alpha_{2}} \right)}} + \ldots + {\left( {r_{n + 1} - r_{n}} \right){\cos \left( {\sum\limits_{1}^{n}\; \alpha_{i}} \right)}}} = R_{e}} & {{Equation}\mspace{14mu} 1} \\{{{nw} + {kw} + {\left( {r_{2} - r_{1}} \right)\sin \; \alpha_{1}} + {\left( {r_{3} - r_{2}} \right){\sin \left( {\alpha_{1} + \alpha_{2}} \right)}} + \ldots + {\left( {r_{n + 1} - r_{n}} \right){\sin \left( {\sum\limits_{1}^{n}\; \alpha_{1}} \right)}}} = r_{n + 1}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

Where r_(n) is the radius of bend for each segment, α_(n) is the bendangle for each segment, w is the width of each segment and R_(e) is thetotal effective radius of bend. All of the r, α and k values areunderstood to be functions of time.

Equation 1 is an obvious geometric requirement and equation 2 resultsfrom the requirement that

${\sum\limits_{1}^{n + 1}\; \alpha_{i}} = \frac{\pi}{2}$

A useful method of applying this principle is to require that theintermediate bend segments r₂, r₃, r₄, . . . r_(n) are held at thenominal value, R_(e) (=nw) (as shown in FIG. 13 for n=2) while adjustingfield values in only the first (i=1) and final (i=n+1) segments of thebend. In this case, the equations simplify significantly. Equation 1becomes,

r ₁(t)+(nw−r ₁(t))cos(α₁(t))+(r _(n+1)(t)−nw)sin(α_(n−1)(t))=nw  Equation 3

and equation 2 becomes

nw+k(t)w+(nw−r ₁(t))sin(α₁(t))+(r_(n+1)(t)−nw)cos(α_(n+1)(t))=r_(n+1)(t)   Equation 4

Equations of similar form to equations 1 through 4 apply to situationswhere the bend angle is other than 90°.

FIG. 14 a shows an ion beam implanter architecture for implanting targetwafers with ions using a deflector according to an embodiment. Animplanter 1200 includes an ion beam source 1440 and analyzer magnet1441. Analyzer magnet 1441 is shown formed from a series of individuallycontrollable electromagnets, which allows for beam focusing, asexplained in more detail below, with reference to FIGS. 17-20. However,analyzer magnet 1441 may also be of a conventional type. Deflectorassembly 1112 is of the type shown and described with respect to FIGS.12 a-12 c. Ion beam 1115 passes from analyzer magnet 1441 throughresolving aperture 1442 into deflector assembly 1112. Deflector assembly1112 is aligned with the axis of incident ion beam 1115. The yoke (e.g.,yoke 1223, not shown in FIG. 14 a) with which deflector assembly 1112mounts is rotatable about the axis of incident ion beam 1115, using arotation drive mechanism 1449. A suitable drive mechanism may be used,such as a servo motor.

Implanter 1200 includes a wafer chuck 1443 for holding and tilting awafer. Wafer chuck 1443 is mounted within a processing vacuum chamber1444 on an arm 1445. Chuck 1443 is tilted under control of a tiltingdrive 1446.

The deflector assembly 1112 provides scanning of beam 1115 in thedirection of incident beam 1115, as described above. FIG. 14 a shows ionbeam 1115 scanned to three different paths, 1115 c, 1115 d and 1115 e.Scanning in a second direction can be achieved by rotating of deflectorassembly 1112 about the axis of incoming beam 1115. The travelingmagnetic field may provide a fast scan at about 10-100 Hz, and themechanical, rotational scan may provide a slow scan at about 0.5 Hz. Theangle through which the rotational scan travels depends on thedimensions of the target and the distance between the target anddeflector assembly 1112. In an embodiment, deflector assembly 1112rotates through +/−25°.

In order to keep the angle between the target surface and beam 1115constant across the scan, wafer chuck 1443 is controlled to rock insynch with rotation of deflector assembly 1112. This motion isillustrated more clearly in FIG. 14 b. FIG. 14 b is a cross sectionalview along the line A-A shown in FIG. 14 a. It can be seen that thewafer can be tilted to maintain ion beam 1115 at normal incidencethroughout the scan. Also shown in FIG. 14 b is a beam dump 1452, towhich beam 1115 is directed when the wafer is being replaced. Beam dump1452 may extend the full length of deflector assembly 1112 and may beused for beam diagnostics. A “straight through” beam measuring assembly1447 is also provided to measure and set up beam 1115, e.g., with thescanner off.

FIG. 14 a also schematically illustrates movement of wafers to and fromwafer chuck 1443. Wafers are loaded into a load lock 1450 through a slitvalve 1451. A wafer transfer assembly 1448 moves the wafer to chuck1443. When the ion implant of the wafer is complete, wafer transferassembly 1448 moves the wafer back to load lock 1450 and the wafer isremoved via slit valve 1451.

FIG. 15 shows a deflector assembly 1560, for deflecting ion beam 1115through an angle of 270°. Each of coil/pole 1561 of deflector assembly1560 is arranged at an angle of 45° to incident beam 1115. Deflectionthrough 270° is useful because particles of a greater range of energiescan be retained in beam 1115. Particles of different energies aredeflected through a different radius of curvature by the magnetic fieldgenerated by deflector elements of assembly 1560, but using thearrangement shown in FIG. 15, they end up traveling on substantiallyparallel paths. Line 1562 shows the effective field boundary where ionbeam 1115 begins to bend. When beam 1115 crosses line 1562 for thesecond time, bending stops. Particles of lower energy may perform atighter bend but still turn through 270°. By contrast, particles ofdifferent energies deflected by about 90° end up on divergent paths.Beam 1115 may be scanned in a direction parallel to incident beam 1115by controlling each of coils 1561 in the manner described with referenceto FIGS. 12 and 13. FIG. 15 shows beam 1115 scanned to two differentpaths, 1115 f and 1115 g.

FIG. 16 a illustrates an electrostatic deflector assembly 1670,according to an embodiment. As shown in FIG. 16 a, electrostaticdeflector assembly 1670 has two parallel arrays of conductive plates1664 disposed above and below the axis of beam 1115—effectively a set ofplates with a slot for the beam to travel. Ion beam 1115 travels betweenthe two arrays, as shown in the cross-sectional view of FIG. 16 b.Corresponding pairs of plates 1664 in each array are held at the sameelectric potential, as indicated by electrical connection 1667, in orderto establish an equipotential plane across the beam gap. Successive(adjacent) pairs of plates 1664 are set at different potentials andeffectively act as electrostatic mirrors and deflect charged particlesas a result of the electric field generated between adjacent plates 1664in each array. The direction of the electric field is shown by lines1665 in FIG. 16 a, and the effective field boundary by line 1666.

In the embodiment of FIGS. 16 a-16 b, plates 1664 are positioned at 45°to incident ion beam 1115. Other angles may be chosen in order todeflect the ion beam through different angles.

By controlling voltage applied to each of plates 1664, deflected ionbeam 1115 can be made to scan in the same manner as described withrespect to deflector assembly 1112, shown in FIGS. 12 a-12 c. Beam 1115is shown in two paths 1115 h and 1115 i in FIG. 16 a. A smooth scan maybe achieved by energizing a plurality of adjacent plates 1664 withineach array at any one time. The same considerations in this regard applyto an electrostatic deflector assembly 1670 as to the magneticdeflector, i.e., deflector assembly 1112.

Electrostatic deflector assembly 1670 of FIGS. 16 a and 16 b may bemounted on a yoke and rotated or translated in the same manner describedwith respect to deflector assembly 1112, e.g., as shown in FIGS. 14 and15.

A deflector assembly according to an embodiment may be used not only toscan a charged particle beam across a target surface, but also to focusan otherwise divergent charged particle beam during a scanning process.The same basic principles can be applied to analyzer magnets (e.g.,magnet 1441) as shown in FIG. 14 a. The analyzer magnet, for example,selects an ion species and provides limited focusing of that species.

FIG. 17 a shows deflector assembly 1112 of FIG. 12, in conjunction withan arrangement of electrodes 1771, 1772, used for decelerating ion beam1115. Some applications may require a particle beam having a high beamcurrent but a low beam energy. At low beam energy, ion beams suffer fromgreater beam divergence due to space charge effects. To minimize thisproblem, the beam can be passed through the implanter with relativelyhigh energy and then decelerated just prior to reaching the target.Assembly 1112 decelerates beam 1115 using a set of retarding electrodes1771, 1772 arranged along the beam path. An electric field generatedbetween electrodes 1772 and electrodes 1771 slows the charged particles.In the embodiment shown in FIG. 17, electrodes 1771, 1772 extend alongthe length of deflector assembly 1112.

When beam 1115 is decelerated, it diverges. The shape of beam 1115without beam focusing is shown in a left beam position 1773, in FIG. 17a. However, deflector assembly 1112 may be controlled to reduce beamdivergence, as shown in a right beam position 1774. In order to reducebeam divergence, particles on the left edge of beam 1115 need to bedeflected through a smaller angle than particles on the right edge ofbeam 1115. By energizing deflecting element coils (e.g., coils 1221,FIG. 12 a) to the left of the centerline of beam 1115 less, and those tothe right of the beam centerline more, a field gradient which is loweron the left and higher on the right is created across the width of beam1115, thus deflecting elements can be controlled to provide a differentbend radius for different parts of beam 1115 while maintaining therequired bending field value at the beam centerline. Similarly, thegradient can be high on the left and low on the right, which willdefocus in the scanning plane but focus in a plane perpendicular to thescanning plane. The result is a focusing condition which can follow thescanning beam. The spatial and temporal distribution of the bendingfield generated by the deflector assembly can be controlled to achievefocusing by varying the amount and duration of the current supplied toeach deflecting element coil. Computer modeling may be used to calculatethe required control strategy, which is dependent on the amount of beamdivergence.

FIG. 18 illustrates how a deflector assembly according to an embodimentcan be used to focus a scanning ion beam without itself performing thescanning function. Since a linearly scanned beam basically forms aribbon, such ribbon beams formed by means other than scanning can alsobe used. Deflector assembly 1112 is of the same type as described withreference to FIGS. 12 a-c. FIG. 18 illustrates beam focusing on threedifferent charged particle (ion) beams 1880, 1881, and 1882. Byproducing a particular field profile within deflector assembly 1112,different parts of the beam (e.g., beam 1115, not shown) can besubjected to different bending fields to provide focusing, which isparticularly easy if the width of the beam as it passes through thedeflector assembly is greater than the width of a single deflectingelement, although this scenario is not a necessary condition forfocusing to work. The three differently shaped beams 1880, 1881, and1882 illustrate the deflector assembly's ability to provide focusingthat is variable with scan position, potentially to correct for beamoptical changes at different parts of the scan range. As a beam isscanned across a target, the focusing field generated by the deflectorassembly can follow the beam to provide the required focusing.

A deflector assembly such as assembly 1112 may therefore providefocusing in the scanning direction. Focusing normal to the scanningdirection can be provided using conventional electrostatic plates.

FIGS. 19 a and 19 b show deflector assembly 1112 of FIG. 18 with adeceleration electrode arrangement 1991, 1992 of the type shown in FIG.17. FIG. 19 b is a cross section of assembly 1112 as depicted in FIG. 19a. As in FIG. 17, two beam positions are shown. A left hand position1993 shows the beam with no focusing, and a right hand position 1994shows the beam with focusing applied.

Another problem with deceleration of an ion beam using electric fieldsis that neutralized ions, which occur in varying degrees in most ionbeam systems, are not decelerated and so will hit the target at higherenergy than desired. Ions can become neutralized at any time afterionization by combining with electrons trapped in the ion beam or strayelectrons in the processing chamber. FIG. 20 is a cross-sectional viewlike that of FIG. 19 b, showing an alternative arrangement ofdeceleration electrodes 2001, 2002, for use with a scanning chargedparticle beam. The deceleration electrodes 2001, 2002 are shaped todeflect a beam of charged particles slightly. Neutralized particles willnot be deflected and so will continue on a straight path and collidewith a neutral stop plate 2003. In the example shown in FIG. 20,deceleration electrodes 2001, 2002 are positioned within deflectorassembly 1112, which represents a possible position providing a compactconfiguration. Electrodes 2001, 2002 may also be positioned subsequentto deflector assembly 1112.

Scanning systems according to an embodiment may be scaled to particularapplications. Large implant work pieces, such as of the order of 2meters in length and larger, are becoming widely used for flat paneldisplays. Also, some solar panel technologies may require ionimplantation of large panels of several square meters in area. Thepresent deflector assemblies are ideally suited for ion implanting onsuch scales. Conventional machines, which move the targets to providescanning, are clearly not well-suited to large work pieces. Existingtwo-dimensional beam scanners would require complicated and highlyaccurate optics to be able to cope with such large work pieces.Applications using electron beams to produce scanning beams of x-rays orother radiation for processing or imaging especially large work piecesare also particularly suited to systems in accordance with the presentinvention.

The present charged particle beam scanning systems offer severaladvantages over conventional scanning systems, such as at least:scanning systems according to the present invention are easily scalablefor different applications; charged particle beams can be variablyfocused throughout a scan; a charged particle beam can be scanned over aplanar surface with the same angle of incidence throughout the scanwithout the need for complicated optics; and the scanning systemaccording to the present invention allows for a compact implanterdesign.

Beam Sweep

The bending of charged particles in a magnetic field is primarilydetermined by the magnetic field strength B, and the distance over whichB is acting upon the particle. The product of these parameters iscommonly referred to as “Bdl” where B is the field strength and dl is“delta length” or distance over which the field is present. A higher Bdlvalue will bend a charged particle of a particular mass and energy moreeither because the B value is higher resulting in a smaller bend radius,or the dl value is higher resulting in a larger bend angle, or both.Scanning of ion beams is commonly achieved by passing the beam through amagnet which has a time varying B field value; as the field goes higherthe bend radius reduces. In such a scanning magnet the dl value remainsapproximately constant. FIG. 21 depicts a scanning (sweep) magnet 2100where the main scanning effect results from time varying of dl. Magnet2100 in combination with a corrector magnets such as 2202 or 2203 may beused within implanter 100, FIG. 1 a, in place of beam deflector assembly13, and similarly used within other exemplary implanter embodimentsdisclosed herein. An ion beam 2115 is directed between the poles pairsof scanning magnet 2100 formed by an array of magnet poles 2101-2105(each with its own set of energizing coils as described previously). Ifno energizing is applied to any of the poles 2101 to 2105, the fieldwill be zero and the beam will pass straight through (2115 a). With polepair 2101 energized to a field value B, the beam 2115 is bent andemerges per 2115 b. With pole pair 2102 energized to the same value as2101, dl is now approximately doubled and the emerging beam positionmoves to 2115 c. Similarly, if pole pair 2103 is energized to the samevalue as 2101 and 2102, the dl is approximately three times and the beamwill emerge at 2115 d, and so on. In this example, beam 2115 will stepfrom one “fixed” position to the next, determined by the dl incrementcontributed by each pole pair. This step can be smoothed out by rampingthe B value up or down in a controlled manner such that the effective dlcontinuously grows between the finite steps determined by the poles2101-2105.

If a work piece is placed in a manner to intercept beams 2115 b-2115 f,the work piece will be impinged by the beam at significantly differentangles as it scans. In many cases this result is undesirable, andscanned beams are usually subject to a further ion-optical element tobring the beam scan parallel. FIG. 22 shows scanning magnet 2100 inconjunction with a second “corrector” pole array 2202. Magnets 2100 andcorrector pole array 2202 may be used within implanter 100, FIG. 1 a, inplace of beam deflector assembly 13, and similarly used within otherexemplary implanter embodiments disclosed herein. In this arrangement,the bend radius within array 2202 varies from left to right with alarger radius at 2215 a, and a smaller radius at 2215 b. The dl value in2202 is approximately constant, and the graduation of bend radiusrequired can be achieved by profiling B. Simultaneously, gradients of Bacross the beam width can be introduced to provide some beam focusing,as discussed above, to control beam spot size and incident angle on thework piece. Scan uniformity can be controlled by profiling the scanspeed.

In FIG. 23, the scanning magnet 2100 is arranged in conjunction with acorrector magnet 2302 of a conventional type. Magnet 2100 and correctormagnet 2302 may be used within implanter 100, FIG. 1 a, in place of beamdeflector assembly 13, and similarly used within other exemplaryimplanter embodiments disclosed herein. This type of corrector uses afixed (not time varying) field and dl is also fixed although one or bothof dl and B are usually graduated over the scan width to achieve beampositions 2315 a through 2315 b.

It should be noted that, although relatively simple magnet shapes areused to illustrate the novelty and advantages of pole array magnets forbeam management, actual designs may incorporate more complicatedfeatures, without departing from the scope hereof. Although the polearray magnet devices (2100, 2202) described herein are disclosed for usewith scanning beams, many can be applied to ribbon beams. Corrector 2202illustrates such an example.

Shelf Shielded Magnet

High voltages associated with the generation and management of beams ofcharged particles are frequently of large enough magnitude thatX-radiation (X-rays) is unavoidably generated. Measures must be taken tocontain the X-rays which otherwise can represent a serious health hazardfor people using the equipment. Ion sources are a typical source ofX-rays and extensive shielding using materials with high atomic numberssuch as lead or tantalum is usually required in the vicinity of the ionsource, and especially around beamline components immediately downstreamfrom the ion source, such as an analyzing magnet. Significant shieldingmaterial costs, plus the important need for radiation safety, often leadto costly X-ray monitoring and interlock equipment to ensure that theequipment is not run accidentally without shielding in place.

In a typical ion beam generation system, the ion beam which originatesfrom the ion source is directed immediately into an analyzingelectromagnet which separates unwanted beam constituents. The magneticflux created between the iron poles by the excitation of the electriccoils is coupled through an iron “return yoke” which is usually quitemassive, and thus able to contribute to X-ray attenuation if it wassuitably configured. However, in traditional designs the return yoke isconfigured so that it provides very limited shielding, losing anadvantage in cost and complexity regarding radiation management. FIG. 24shows one exemplary x-ray shielding analyzer magnet 2400. FIG. 25 showsa cross section through analyzer magnet 2400. Analyzer magnet 2400 maybe used within implanter 100, FIG. 1, in place of analyzer magnet 12,and may be similarly used in other implanters disclosed herein. Inanalyzer magnet 2400, the magnet return yoke is configured as a largelyclosed iron box in order trap X-rays injected into the magnet from theion beam source port 2425. Another advantage of this configuration isthat the iron box also functions as the vacuum housing which istraditionally a separate assembly, further reducing costs andsimplifying the overall assembly.

The magnet illustrated has a bend angle of 60 degrees, but could be anyvalue. Typical analyzer magnet bend angles range from 30 to 120 degrees.FIG. 24 is a section through the median plane of the magnet and showsthe return yoke/vacuum box wall surrounding the 60 degree pole. Forclarity, the beam 2415-2415 a is depicted without illustrating theseparated, unwanted beam constituents which bend through angles that aremore or less than the main beam, and consequently can be blocked and notdelivered to the exit port 2426. The poles 2421 are shaped to producethe required magnetic field configuration and are magnetically connectedto the return yoke via iron cores 2527. The energizing coils 2523 areshown in a non-magnetic hermetic housing 2402 so that they do notoperate in vacuum, and electrical and cooling connections can be easilymade via small ports 2503. Optionally, the coils can be mounted in avacuum and each connection individually hermetically sealed. FIG. 25 isa section through the centerline of FIG. 24 and thus shows the completemagnetic flux path as well as emphasizing the closed box configurationof the return yoke. Iron is not as effective as lead for X-rayshielding, but in many cases the iron thickness will be sufficient orcan be easily adjusted so that no additional shielding material isrequired. Generally, it will be much more cost effective to increase theyoke thickness beyond the requirement of the magnetic flux alone ratherthan add separate additional shielding.

Other sources of X-rays such as those generated from accelerator gapscan be managed by variations on this basic concept including focusingmagnets such as quadrupole, sextupole, and steerer designs, which employan external box structure return yoke and/or vacuum housing.

Spin Scan

More efficient utilization of the ion beam in the present system hasother significant advantages. In an ideal scanning method, the beamwould only impinge on the wafer chuck (work piece) and none of the beamwould be wasted by over-scanning. However, in practice, the beam mustnot reverse direction while on the wafer because an over-exposure willoccur at the turn-around point, since the beam must come to rest for amoment. In principle, superior beam utilization is achievable byspinning the wafer around its own center, combined with linear scanningof the beam spot along a diameter or parallel to a diameter. Thisgeometry has an inherent problem that a singularity occurs at the verycenter (of rotation) of the wafer and an overdose results at that point.Techniques have been proposed to mitigate this problem and are not partof the scope of this invention.

FIGS. 26 and 27 describe a very simple implanter 2600 with an absoluteminimum of components, achieved by combining a spinning wafer chuck 2614(work piece) with the angular scan previously described to implement thelinear scan. Implanter 2600 includes a wafer transfer assembly 2618, aprocessing vacuum chamber 2616, a tilting drive 2617, an ion beam source2610 generating an ion beam 2711, a “straight through” beam measuringassembly 2620, a rotation drive mechanism 2615, a load lock assembly2619, and a beam dump 2721. A single 90 degree magnet 2650 is used asboth an analyzer magnet and angular scanning device.

An alternative spin-scan implementation can be applied to implanter 100,FIGS. 1 a and 1 b, by enabling the wafer chuck 2614 to spin andutilizing the beam deflector assembly 13 to achieve the linear scanacross the wafer. In this case, angular scanning of deflector assembly13 would not be required. The embodiments disclosed herein, which effectlinear scanning of the beam by travelling field or other methods, may beused in conjunction with wafer spinning.

Split Pole

An aspect of travelling field beam scanning is the change in path lengthtravelled by the beam from one scan extent to the other. Since ion beamparticles carry like electrical charges, they repel each other leadingto “space charge expansion” of the beam as it progress. In general, thefarther a beam travels, the larger it will become. A large change inbeam spot size over different parts of the wafer (work piece) isundesirable. The spot (beam) size is usually controlled by focusingelements such as quadrupole magnets or electrostatic lenses. In the casewhere the beam path length varies, focusing must be dynamic and followthe beam scan (path length change). FIG. 28 shows one exemplaryembodiment of a deflector assembly 2812 where some of the magnet poles2824 which are energized by controlling the electric current in coils2821 are split at the incoming beam 2815 centerline and each of thesmaller poles 2824 a and 2824 b is individually energized by controllingthe current in coils 2821 a and 2821 b. Deflector assembly 2812 may beused within implanter 100, FIG. 1 a, in place of beam deflector assembly13, and similarly used within other exemplary implanter embodimentsdisclosed herein. When the split pole sets 2824 a and 2824 b areenergized together they act upon the beam in a manner essentiallyidentical as a single pole set 2824. As the scanned beam progresses from2815 a to the longer path length 2815 b, the input pole sets aresuccessively turned off as described elsewhere and no longer play a partin the scanning action. If a split pole set 2824 a and 2824 b isenergized with opposite polarity, the magnetic field at the beam inputcenterline can be maintained at zero so no bending (scanning)contribution takes place, but left and right of the centerline a fieldof increasing/decreasing value occurs. The quadrupole field formed inthis way can be used to apply focusing to compensate for the beam spotsize change arising from the increasing path length.

FIG. 29 shows one exemplary ion implant apparatus 2900 formulti-directionally scanning a beam of charged particles across a targetsurface, according to an embodiment. The basic architecture of apparatus2900 is similar to that shown in FIG. 5 a, and like elements areindicated using the same reference numerals.

Apparatus 2900 includes beam scan electrodes 2932 (for example, a pairof parallel electrode plates) positioned around ion beam 11, betweenresolving aperture 2916 and a deflector 2931. Deflector 2931 may differfrom deflector 53 of FIGS. 5 a and 5 b. In one aspect, deflector 2931 isformed with two pairs of parallel nested electrode plates which areshaped as sections of toroidal surfaces of predetermined radii. The formof deflector 2931 is clarified in FIGS. 38, 39, and 40. FIG. 38represents a doughnut or toroid shaped metal tube 3820 centered at point3823. A section A-A through tube 3820 reveals a second nested tube 3921that is symmetrical with toroid shaped metal tube 3820, as shown in FIG.39. If toroid shaped metal tubes 3820 and 3921 are cut through planesA-A, B-B, C-C, and cylindrical surface D-D a sector of the toroidassembly representing deflector 2931 is left, as shown in FIG. 40deflecting beam 11 through 90° to form beam 4011 a. In this simplifiedexplanation, the resulting sector is illustrated as ninety degrees,although a smaller angle sector is shown in FIG. 31. Alternatively,deflector 2931 includes a pair of nested conical plates with the frontplate gridded or slotted to let the beam in and out form an elongated,curved electrostatic mirror.

A variable electric field is generated between beam scan electrodes2932, to scan ion beam 11 in a first direction normal to the axis of thebeam 11 in a plane parallel to surface D-D. The scan centroid is locatedat the center point 3823 of the toroid deflector 2931. Deflector 2931 isshown deflecting beam 11 to three different positions, 11 a, 11 b, and11 c. Deflector 2931 deflects beam 11 such that beam 11 a/b/c emergesfrom deflector 2931 in an arcuate scan-line of radius determined by theradius of the toroidal surfaces, provided that it is deflected byprecisely 90 degrees by deflector 2931 and that it enters deflector 2931along a radius of the toroidal surfaces in the plane of the firstdirection. This condition may be maintained at all times throughout thescan by beam scan electrodes 2932, illustrated in FIGS. 30 and 31. Aslit valve 2924 is a vacuum valve with a slit opening matching the sizeof wafers and which operates to isolate loadlock 19 from atmosphere.

FIGS. 30 and 31 are cross-sections through beam deflector 2931 and beamscan electrodes 2932. In particular, FIG. 30 is a cross-section in thedirection A-A shown in FIG. 29. FIG. 31 is a section in the directionB-B shown in FIG. 29. The shaded area in FIG. 31 indicates passage ofion beam 11 as it exits deflector 2931. Position of wafer chuck 14 isshown in dotted outline. Beam scan electrodes 2932 provide for scanningof ion beam 11 in a first direction. Translation of deflector 2931 andbeam scan electrodes 2932 along the axis of incoming beam 11 facilitatescanning of beam 11 in a second direction. In this embodiment, rotationof deflector 2931 is not necessary. However, a rotational drive (e.g.,linear and rotational drive mechanism 55) may be included to direct beam11 to different target wafers positioned around deflector 2931 or to abeam dump 3025.

FIGS. 32 and 33 show an alternative beam scanning arrangement 3200,according to an embodiment. FIG. 32 schematically shows an ion beamsource 3250 producing an ion beam 3252. FIG. 33 is a cross section ofarrangement 3200. Ion beam 3252 leaves ion beam source 3250 and enters amagnetic beam scanner 3251. Ion beam 3252 passes through a magneticfield inside magnetic beam scanner 3251, and is deflected by themagnetic field. Different magnetic field strengths deflect ion beam 3252through different angles. The magnetic beam scanner 3251 includes anelectromagnet or electromagnets which can be electrically controlled. Byaltering the magnetic field in beam scanner 3251, ion beam 3252 may bescanned through an angular range in a first plane.

Scanned ion beam 3252 leaves magnetic scanner 3251, passes through aresolving aperture 3254 and enters a deflector 3253. In one aspect,deflector 3253 has two pairs of electrode plates (described withreference to FIGS. 5 a and 5 b) and acts to deflect ion beam 3252 out ofthe first plane. Deflector 3253 is moveable to and from magnetic scanner3251 along the line of emergent ion beam 3252, to provide scanning Inorder to align with emergent ion beam 3252, both resolving aperture 3254and deflector 3253 are moveable in an arc. The movement of deflector3253 and resolving aperture 3254 is electronically controlled inconjunction with the magnetic field in scanner 3251. Magnetic scanner3251, for example, provides a fast scan while the mechanical radialmovement of deflector 3253 provides for slow scanning.

FIG. 34 depicts a beam scanning arrangement 3400, according to anembodiment. Scanning arrangement 3400 includes two deflectors 3460, 3461of the type described with reference to deflector beam deflectorassembly 53, FIG. 5 a. First deflector 3460 is rotatable about incomingion beam 3452. First deflector 3460 has of two pairs of parallel plates,which are, for example, sections from the surface of a sphere of apredetermined radius. First deflector 3460 is shown in differentpositions, indicated by dotted outline, when rotated about an axis ofrotation. Target wafer chuck 14 is also shown.

Second deflector 3461 is shown in a central position in full line, andadditionally illustrated in four alternative positions, by dotted lines.Second deflector 3461 is translatable to and from first deflector 3460,parallel to ion beam 3452 output from first deflector 3460. An electricpotential is set up across the pairs of plates to provide an electricfield, which deflects on ion beam 3452 through 90° so that it travelsparallel to its initial direction, as is shown in FIG. 35. As shown,both first and second deflectors 3460 and 3461 deflect the ion beamthrough 90°. However, deflectors 3460 and 3461 may deflect ion beam 3452through other angles and still provide a two dimensional parallel scan.

FIG. 35 shows first and second deflectors 3460, 3461 in cross-section.First and second deflectors 3460, 3461 are each shown as two pairs ofparallel electrode plates. Alternative positions of second deflector areillustrated by dotted lines. Second deflector 3461 may be mounted on atrack (not shown) connected with first deflector 3460. The track andsecond deflector 3461, for example, rotate with the first deflector3460. Second deflector 3461 may be moved to and from first deflector3460 along the track using any suitable driving means, such as a linearmotor. Alternatively, deflectors 3460 and 3461 may be magnetic. Forexample, a magnetic deflector 3460 may be useful with low energy beams.

FIG. 36 illustrates a method 3600 for scanning a beam of chargedparticles in two non-parallel directions. In step 3602, a beam ofcharged particles is generated. For example, ion beam source 10 andinjector assembly 2911 of ion implant apparatus 2900, FIG. 29, form anddischarge ion beam 11. In step 3604, the beam of charged particles isscanned in a first direction. In one example of step 3604, beam 11 isscanned across the surface of a wafer held in wafer chuck 14. In step3606, the beam is scanned in a second direction, non-parallel with thefirst direction. For example, deflector 2913 is translated and/orrotated via drive mechanism 55 to deflect beam 11 and scan the beam inthe second direction.

FIG. 37 shows an exemplary method 3700 for multi-directional scanning ofa charged particle beam. A charged particle beam is generated, in step3702, and scanned in a first direction in step 3704. In one example ofsteps 3702, 3704 shown in FIG. 29, ion beam source 10 produces beam 11.Beam 11 is discharged from injector assembly 2911 and scanned along thebeam axis. In step 3706, the beam is deflected towards a target surface,using a beam deflector. For example, beam 11 is received at deflector2931, which deflects the beam towards the surface of a wafer held inwafer chuck 14. In step 3708, the deflector is moved linearly to scanthe beam across the target surface, in a second direction. In oneexample of step 3708, drive mechanism 55 is actuated to rotate deflector2931 and re-direct beam 11 across the surface of a wafer held at chuck14.

Steps 3710-3714 are optional, as indicated by dotted box 3709. In step3710, the target surface is tilted based upon deflector position, toachieve a desired angle of incidence between the beam and the targetsurface. In one example of step 3710, tilting drive 17 tilts wafer chuck14 to change position of a wafer held therein, according to a desiredangle of incidence.

In steps 3712 and 3714, the deflector is rotated to direct the beam to asecond target surface, and the beam is scanned parallel to the incidentbeam axis. In one example of steps 3712 and 3714, deflector 2931 isrotated via drive mechanism 55, to direct beam 11 to a second targetsurface, and beam 11 is then scanned across the target surface in adirection parallel to the axis of incident beam 11.

It will be understood that certain changes may be made in the abovesystems and methods without departing from the scope hereof. Thus, it isintended that all matters contained in the above description or shown inthe accompanying drawings are to be interpreted as illustrative and notin a limiting sense. One of ordinary skill in the art will appreciatethat similarly named parts in the above embodiments may represent partshaving similar structure and functionality, unless otherwise describedherein. For example, ion beam source 10, FIG. 1, may be similar to ionbeam sources 810, 1110, 1440 and 2610 of FIGS. 8 a, 11, 14 and 26,respectively. It is also to be understood that the following claims areto cover generic and specific features described herein, and allstatements of the scope of the invention which, as a matter of language,might be said to fall therebetween.

1. A system for scanning a beam of charged particles across a targetsurface comprising: a beam source for producing a beam of chargedparticles along an incident beam axis; a beam deflector, positioned onthe incident beam axis, for deflecting the beam of charged particlesaway from the incident beam axis towards the target surface; and arotation mechanism coupled to the beam deflector to rotate the beamdeflector about the incident beam axis.
 2. The system of claim 1, thefurther comprising a wafer holder for holding a target wafer having thetarget surface, the wafer holder configured for tilting the wafer tofacilitate impingement of the beam upon the target surface. 3.(canceled)
 4. The system of claim 2, further comprising a tiltcontroller for controlling tilt of the wafer as a function of arotational position of the beam deflector, to maintain a predeterminedangle between the beam of charged particles and the target surfacethroughout a scan.
 5. The system of claim 1, further comprising a firstwafer holder and a second wafer holder, the rotation mechanismconfigured for rotating the beam deflector to selectively direct thebeam of charged particles towards the first wafer holder or the secondwafer holder.
 6. The system of claim 1, further comprising beam scanningmeans for scanning the charged particle beam in a directionsubstantially parallel to the incident beam axis. 7.-12. (canceled) 13.The system of claim 1, the beam deflector comprising one of anelectrostatic deflector, a pair of curved electrode plates, and amagnetic deflector.
 14. The system of claim 1, further comprising asecond ion beam source for producing a second beam of charged particles.15. The system of claim 14, further comprising an analyzer magnetcorresponding to the ion beam source and a second analyzer magnetcorresponding to the second ion beam source.
 16. The system of claim 1,the beam deflector comprising a scanning magnet and a corrector magnet.17. The system of claim 16, the corrector magnet comprising a magnetwith a fixed field.
 18. The system of claim 16, the corrector magnetcomprising a pole array.
 19. The system of claim 1, the beam sourcecomprising an x-ray shielding analyzer magnet.
 20. The system of claim1, the beam deflector comprising a magnetic array having a plurality ofpoles, wherein at least one of the plurality of poles is split at thecenterline of the beam.
 21. A method for scanning a beam of chargedparticles across a target surface, comprising the steps of: providing abeam of charged particles along an incident beam axis; providing a beamdeflector on the incident beam axis, for deflecting the beam of chargedparticles away from the incident beam axis towards the target surface;and rotating the beam deflector about the incident beam axis to scan thebeam across the target surface.
 22. The method of claim 21, furthercomprising the step of tilting the target surface depending on arotational position of the beam deflector, to maintain impingement ofthe charged particles upon the target surface at a predetermined anglethroughout a scan.
 23. The method of claim 21, further comprising thestep of rotating the beam deflector to direct the beam to a secondtarget surface.
 24. The method of claim 21, further comprising the stepof scanning the beam in a direction substantially parallel to theincident beam axis.
 25. The system of claim 1, further comprising: afirst wafer holder for holding a target wafer; and a second wafer forholding a target wafer; wherein the rotation mechanism rotates to directthe beam at the first wafer holder and the second the wafer holder. 26.The system of claim 1, further comprising: a dual-chuck system forholding and transferring wafers through ion implantation, having: aturntable controllable via a turntable rotational mechanism; a first armextending from the turntable; a second arm extending from the turntableand disposed opposite the first arm; a first chuck configured with thefirst arm, for holding a first workpiece; a second chuck configured withthe second arm, for holding a second workpiece; and at least one tiltmechanism for tilting one or both of the first and second arms, to varyan angle of the first or second chuck and workpiece, during ionimplantation; wherein the turntable rotational mechanism rotates toposition the first chuck for scanning of the first workpiece with thedeflected beam, while positioning the second chuck for loading orunloading of the second workpiece. 27-31. (canceled)
 32. An implanterarchitecture, comprising one or more loadlocks, for accepting andtransferring workpieces; a vacuum transfer, for transferring theworkpieces from the loadlock; and a plurality of ion beam implanters foraccepting the workpieces from the loadlock; each ion beam implanterhaving: a dual chuck system for simultaneously holding two workpieces,mounted on opposing arms of the dual chuck system, and transferring theworkpieces through ion implantation; an ion source for producing an ionbeam along an incident beam axis; a beam deflecting assembly forreceiving and deflecting the ion beam towards the workpieces mountedwith a first of the opposing arms; and a rotation mechanism coupled tothe beam deflecting assembly for rotating the beam deflecting assemblyabout the incident beam axis. 33.-67. (canceled)